In the prior art several methods are known for rejuvenating bitumen containing compositions. An example thereof is disclosed in R. Romera, Project 1992-1993/ISSN 0361-1981, Transportation Research Board of the National Academies, Spain, “Rheological Aspects of the rejuvenation of aged bitumen”, Jun. 27, 2005. Herein the following rejuvenation additives have been tested: commercial aromatic oil, aromatic motor recycling oil, and Soft 150/200 Penetration Bitumen. Research showed that the best composition contained 80% aged bitumen in combination with 20% motor oil. No cashew nut shell oil is mentioned.
Also WO/2008/084014, in the name of Shell Internationale Research Maatschappij BV at the Hague (NL), discloses a rejuvenating agent and a method for recycling asphalt. As a rejuvenating agent a composition is used comprising bitumen and palm oil.
Examples of other known rejuvenating agents from the prior art are paraffins and rape seed oil etc. However these agents have just like palm oil the important disadvantage that they render the bitumen too soft, whereby the viscosity of the bitumen containing composition, such as for example asphalt, becomes also too low. In the case of for example asphalt because of these agents the adherence to the aggregate is decreasing whereby the durability of the asphalt is being impaired. Also these agents are poorly mixable with the bitumen.
Further petrochemical resins exist which can be used as rejuvenating agents for bitumen containing compositions, although these are very expensive.
In the prior art it is known to recycle asphalt and other bitumen containing compositions. Hereto the compositions usually are milled and added to new compositions to be prepared or are recycled as such while adding suitable additives. In this case always also new fresh bitumen has to be added to the composition to guarantee the processability and quality (durability, life) of the composition. In other words, compositions being comprised of solely recycled bitumen containing material with good properties for use in practice showed to be impossible up till present. Although such compositions exist these are applied where the inferior properties thereof are not important. For example machined asphalt is reused without the addition of fresh bitumen for road side reinforcement edges. Such a material is however fully unsuitable for use as new road surface.
The amount of available suitable bitumen is decreasing considerably in recent years. This is a consequence of the fact that petroleum is distilled at increasing temperatures whereby less and less heavy fraction remains. Furthermore heavy fractions are upgraded to obtain more useful and therefore more valuable products. The amount of available bitumen thereby not only decreases but also the quality is getting worse. Nowadays because of that bitumen is even prepared new from other chemical substances.
Bitumen containing compositions are very sensitive to aging and therefore have to be replaced in time as the properties in time degrade. Ageing of bitumen containing compositions can be caused by different mechanisms, comprising oxidation, evaporation of substances, UV-attack, exudation and orientation. In this process partly maltenes are converted into asphaltenes, whereby the material gets more brittle. By ageing the favorable properties for processing and application decrease in quality. The compositions frequently become harder, more brittle, less flexible and in time less and less recyclable.
Bitumen is for the majority used in asphalt for road construction. By erosion and weather influences asphalt ages relatively quick and usually asphalt has to be renewed within ten years. Hereto the asphalt is removed from the road surface and decreased in size by milling. This milling product is recycled with new asphalt preparation in a small amount. Real recycling of such milling asphalt while maintaining good asphalt properties is nowadays only possible with very high cost by for example the additional of special chemical substances or fresh bitumen.
In the prior art therefore a demand exists for a method for rejuvenating bitumen, such that old bitumen containing compositions can be recycled. Up till present this appeared not or only on a very costly manner to be possible.